How to change default finger motions on valve index?

Hello all, I’ve got an avatar that has a second thumb and I’m having trouble getting it to act the way it should. What I’d love to have happen is when I close my pinky finger around my index controller, to have the second thumb close like a thumb would. If i simply set the second thumbs bones to the pinky bones in unity then the thumb just closes like a finger would. What I mean is that, the thumb will close downward and towards the wrist. Whereas I’d like it to close more like a thumb would where it closes sort of inward towards the palm or across the palm rather than straight down.

Essentially think of what’s happening as if you were to take a finger from the top of your hand and without rotating it at all, attach the side of the first knuckle to the spot where your thumb joins your hand. Closing that finger just makes it curl up down and under you hand.

Does anyone know how to override the default motions from the valve index controller finger tracking? Or alternatively, how I might link (via constraints in unity) the second thumb bones to a normal non-weighted set of pinky finger bones that would mimic the type of closing motion I’d like?